In most electronic devices there is generally a tradeoff between performance and power consumption. In particular, faster or enhanced performance generally requires more power. In battery-powered devices, increased power consumption therefore generally means shorter battery life for the device. Portable and other electronic devices that rely on a battery power supply have become more prevalent. Correspondingly, management of power consumption issues has become increasingly important.
Maximum performance can be a priority for many electronic devices and applications. For battery-powered devices, however, the amount of power consumed may be more important to the user than the performance or speed of the device. For example, a mobile phone user may accept lower performance in exchange for less power consumption and thus longer battery life. Similarly, a user of a portable computer may accept slower performance in exchange for longer battery life. Accordingly, some electronic devices incorporate various operational modes that allow for intelligently reducing performance to conserve power and to extend battery life.
Most electronic systems and devices today incorporate some kind of memory storage system. Generally, the host system uses the memory storage system to store data for retrieval later. Often the internal transfers of data within a memory storage system can occur at rates much faster than the transfer rates of the data to the host seeking the data (or faster than the rate the host can use the data). The difference in data transfer rates for the internal memory system versus the interface rates to a host seeking access to the memory system can be substantial. As a result, the storage system is often capable of supplying data to the host faster than the host can receive or use it. Such a mismatch in transfer rates can occur if the host is set to operate at a slower speed to conserve power. If the host speed is slowed down to conserve power, the mismatch between the transfer rates for the host and the storage system may be exacerbated.
A mismatch in the transfer rates of the host and the storage system can result in delays when the storage system waits for the host to catch up. Stalling or idling the storage system to accommodate the host transfer rate does not necessarily affect performance, since the throughput would still equal the host transfer rate. Having a substantial subsystem such as the memory storage system sitting idle, however, can have deleterious effects on power consumption and efficiency.